The invention relates to data storage media and, more particularly, to techniques for marking data storage media.
Magnetic media are a popular form of data storage media, and are used for storage and retrieval of data. Magnetic media come in many forms, such as magnetic tape and magnetic disks. A write/read head assembly, which includes one or more write/read transducer heads, writes data to and reads data from the magnetic medium. The data stored on the medium are usually organized into xe2x80x9cdata tracks,xe2x80x9d and the transducer heads write data to and read data from the data tracks.
Data tracks on magnetic tape are generally parallel to each other, and often are oriented substantially longitudinally on the tape. The head assembly is usually oriented transverse to the path of the magnetic tape so that the transducer heads move transversely across the width of the tape to access the tracks. On a magnetic disk, the data tracks are generally arranged as concentric circles or a spiral pattern on the disk, and the head assembly typically moves along a radius of the disk to access the tracks.
For efficient reading and writing, a transducer head must be accurately positioned to read from or write to a particular data track. A servo control loop typically is provided to control the positioning of the head relative to the data tracks. The medium often includes specialized tracks, called xe2x80x9cservo tracks,xe2x80x9d to serve as references or landmarks for the servo. Data tracks can be located on the magnetic medium according to the displacement of the data tracks from one or more servo tracks.
Servo tracks may include magnetic markers, in which case the surface of the medium is homogeneous but the servo track can be detected magnetically. Another type of servo track is a physical mark on the medium, such as a groove. With this type of servo track, the medium surface is not homogeneous but is physically altered at the site of the servo track. Servo tracks of the latter type can be detected optically. The groove may be discontinuous, allowing an optical sensor to detect a groove signal when a groove is sensed and a reference signal when the groove is absent.
Because servo tracks serve as markers, it is important that the servo tracks be placed on the medium with precision and accuracy. For example, servo tracks on magnetic tape are typically straight and servo tracks on a magnetic disk are nearly perfect circles. A deviation from the ideal shape of a servo track may compromise the effectiveness of the servo track as a marker.
The invention is directed to techniques for creating tracks, such as physical or magnetic marks, on a data storage medium such as magnetic tape. The physical marks can be used, for example, as servo tracks, and can be detected optically.
The invention will be described in reference to magnetic tape, but the invention is not limited to that particular data storage medium. The invention may be applied for use with other magnetic and optical data storage media.
In one embodiment, the invention presents a system that includes one or more sensors, such as edge detectors, that detect the position of a data storage medium. The system also includes a marking device that marks a track on the data storage medium, such as a laser that ablates a physical track. The system further includes an actuator that causes the marking device to mark the track as a function of the position detected by the sensor. The data storage medium may be a magnetic storage medium, but the invention encompasses other data storage media as well.
In another embodiment, the system presents a method, which includes moving a data storage medium past a marking device, sensing the position of the data storage medium and marking a track in the data storage medium as a function of the sensed position. Sensing the position of the data storage medium may include, for example, sensing an edge of the data storage medium. Marking a track in the data storage medium may include, for example, ablating a track in the data storage medium with a laser.
In a further embodiment, the system presents a method, which comprises receiving a position signal indicative of the position of a data storage medium and generating a control signal as a function of the position signal. A marking device marks a track in the data storage medium as a function of the control signal. This method may also employ feedback and/or feed-forward techniques to direct the marking, which may be performed by ablating with a laser beam.
The details of one or more embodiments of the present invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present invention will be apparent from the description and drawings, and from the claims.